Hmm... should definitely be added... I'm amazed this hasn't been asked before...The only problem with it is that many themes might get messed up if you place an extra line of text there... but I do think people should definitely be given the option.

Btw, [Unknown]'s suggestion causes a long invisible clickable area that collapses the category, which categories without descriptions don't have (display:block is the culprit). This snippet does it in a cleaner way (and uses the forum theme .css file!):Encoding<span class="smalltext" style="font-weight:normal;"><br>The techie stuff.</span>